1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly to a method and a system for solving inconsistency in PLMN (Public Land Mobile Network)-related information between a user equipment and a network, which can occur in an environment where the user equipment hands over from an RAT (Radio Access Technology) area to an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) area which has a different PLMN from that of the RAT area.
2. Description of the Related Art
3GPP (3rd Generation Partnership Project) which is representative of general mobile communication systems, defined an EPS (Evolved Packet System) and introduced an MME (Mobility Management Entity) as a mobile manager of a network, for the next generation communication. In addition to such a change in a communication core network (i.e. a change to an EPS), wireless access technology introduced an E-UTRAN. The mobile communication system as described above improved a Non-Access Stratum (NAS) protocol used in a conventional mobile communication system (particularly, 3G of 3GPP), and proposed an improvement method in order to provide high-speed communication services in the next generation mobile communication. Herein, in addition to a previously-performed authentication process and a security process performed in a wireless access layer, a security mode was performed by introducing a secured NAS protocol concept to a NAS layer. Accordingly, a security management method was strengthened. Also, in order to promote the efficiency of the wireless access technology, the wireless access technology was designed in such a manner as to avoid overhead in a wireless connection message even at an RRC (Radio Resource Control) side. Accordingly, a NAS protocol determines that when a user equipment hands over, information such as a PLMN identity is transmitted through tracking area update accept.
However, currently, according to the definition of the NAS protocol, the definition of ISR and the definition of a network sharing environment, in supporting handover between PLMNs, currently-defined procedures and messages can cause a problem such that communication may be cut off in an actual operation of the handover, or a problem of security. Accordingly, it is necessary to propose a method which continuously and efficiently performs authentication, the support of security and the support of communication between a user equipment and a network even in an environment, where a PLMN changes, through improvement in network sharing and an ISR handover process.